Photographic material comprising a silver halide element with an overlayer of gelatin hardened with mucochloric acid

ABSTRACT

THIS APPLICATION DESCRIBES PHOTOGRAPHIC MATERIAL SUITABLE FOR USE FOR THE PRODUCTION OF GLAZED PRINTS, WHICH MATERIAL COMPRISES IN THE UNEXPOSED AND UNPROCESSED STATE A SUPPORT BASE HAVING COATED ON A LEAST ONE SIDE A GELATINO SILVER HALIDE EMULSION LAYER THE SAID GELATIN HAVING BEEN HARDENED BY THE PRESENCE OF FORMALDEHYDE THEREIN, THE IMPROVEMENT THAT THERE IS COATED ON THIS LAYER A GELATIN SUPERCOAT LAYER WHICH HAS BEEN HARDENED BY THE PRESENCE OF MUCOCHLORIC ACID THEREIN.

United States Patent 3,697,278 PHOTOGRAPHIC MATERIAL COMPRISING A SILVER HALIDE ELEMENT WITH AN OVER- LAYER 0F GELATIN HARDENED WITH MUCOCHLORIC ACID Albert Edward Harris and Ian Blundell, llford,, Essex, England, assignors to Ilford Linn'ted, Ilford, England Np Drawing. Filed Apr. 10, 1969, Ser. No. 815,218

Int. Cl. G03c 1 76 US. Cl. 96-67 5 Claims ABSTRACT OF THE DISCLOSURE This application describes photographic material suitable for use for the production of glazed prints, which material comprises in the unexposed and unprocessed state a support base having coated on at least one side a gelatino silver halide e'mulsionlayer the said gelatin having been hardened by the presence of formaldehyde therein, the improvement that there is coated on this layer a gelatin supercoat layer which has been hardened by the presence of mucochloric acid therein.

This invention relates to photographic material and in particular to photographic material suitable for the prodhction of photographic prints and to photographic prints.

Photographic prints are usually made from photographic paper which material usually comprises a base of higli-wet strength paper containing fillers having on one side a white reflective layer such as a baryta layer, i.e. finely divided barium sulphate in a colloid binder for example gelatin, there being coated on the reflective layer a gelatino silver halide emulsion layer which in turn has coated on it a gelatin supercoat or protective layer. Usually both the silver halide emulsion layer and the supercoat layer are hardened by incorporating a hardening agent such as formaldehyde in each layer and allowing it to cross-link the gelatin.

Photographic: prints usually have either a glossy surface or a matt surface. The matt surface may be achieved by using a rough-surfaced paper while a glossy surface is generally achieved by using a smooth-surfaced paper. However in the case of glossy prints, in order to obtain a high gloss it is essential to glaze the final print. The action of glazing comprises placing the gelatin coated surface of the print material, of which at least the supercoat layer is in the swollen condition, into intimate contact with a highly polished surface and allowing the print to dry while in this position. The swollen supercoat of the print when placed into intimate contact with the highly polished or glazing surface conforms exactly to the glazingsurface and when the print is dry its surface is highly glazed.

In this operation it is essential that the whole surface of the print is placed into intimate contact with the glazing surface; if it is not the areas of the print which are not in contact with the glazing surface do not become as smooth as the remaining areas and so-called fleck marks are produced. Sometimes areas of the print surface come away from the glazing surface while these areas are still in the swollen state; this also results in fleck marks in such areas. It has been found that photographic material for use in the production of glazed prints wherein the supercoat layer has been hardened by the use of formaldehyde exhibits a tendency for fleck marks to be produced during the glazing process. It is the object of the present invention to provide photographic material suitable for use in the production of glazed prints which exhibits a decreased 3,697,278 Patented Oct. 10, 1972 tendency for fleck marks to be produced during the glazing process.

According to the present invention there is provided photographic material suitable for use for the production of glazed prints, which material comprises in the unexposed and unprocessed state a support base having coated on at least one side a gelatino silver halide emulsion layer the said gelatin having been hardened by the presence of formaldehyde therein, and coated on this layer a gelatin supercoat layer which has been hardened by the presence of mucochloric acid therein.

The preferred support base is a paper support base and it is preferred that there is present on this support base a reflecting layer such as baryta layer and that the gelatino silver halide emulsion layer is coated on this reflecting layer.

The preferred amount of mucochloric acid present in the supercoat layer to achieve a suitable degree of hardening of this layer is from 0.352% by weight of the gelatin, the most preferred amount being in the range of 1 to 1.5% by weight of the gelatin.

According to another aspect of the present invention there is provided a process for the production of photographic material suitable for use for the production of glazed prints, which comprises coating on a base support a gelatino silver halide layer which comprises sufficient formaldehyde to harden the layer, allowing this layer to set and coating on this layer a gelatin supercoat layer which comprises sufficient mucochloric acid to harden the layer allowing this layer to set and drying the product.

It has been found that when both the silver halide layer and the supercoat layer are hardened with mucochloric acid a certain loss of sensitivity is apparent in the unexposed material and certain other disadvantages are encountered, e.g. the silver halide layer shows a greater tendency to stain during processing.

The following examples will serve to illustrate the invention.

EXAMPLE 1 A chlorobromide emulsion containing formaldehyde as hardening agent was coated on a baryta coated paper support. After this layer had set a supercoat layer was applied which comprised a gelatin solution containing an addition of mucochloric acid at the rate of 1.5 by weight based on the gelatin. After a suitable period to allow hardening to occur samples of the paper were exposed, developed, fixed and washed in the conventional manner. Drying was carried out on a rotary glazing drum with the emulsion layer facing the glazing surface. Satisfactory glazing properties were obtained after several months keeping and also after a period of high temperature storage.

A similar chlorobromide emulsion was prepared containing mucochloric acid as the hardening agent and coated on a baryta coated paper support. A supercoat layer was applied as above.

This photographic material which comprises the emulsion which had been hardened with mucochloric acid was compared to the photographic material which comprises the emulsion which had been hardened with formaldehyde and was found to have a photographic speed of 0.15 log units less than the latter material.

EXAMPLE 2 A sample of Kenprint paper, which is photographic paper manufactured by Ilford Limited and is suitable foruse in an automatic printing and processing apparatus, was prepared in which the photographic emulsion was hardened by the use of formaldehyde and the gelatin supercoat was hardened by treatment with mucochloric acid 3 added to the gelatin at the rate of 1.0% by weight based on the gelatin.

This gelatin layer was then allowed to harden to a melting point suitable for withstanding the hot glazing process. Testswere then performed on continuous processing and glazing equipment wherein the paper was developed, fixed and washed and glazed continuously. Glazing quality was found to be excellent when compared to paper in which the gelatin supercoat had been hardened with formaldehyde.

A fleck mark count on this sample of Kenprint paper (sample 1) was carried out and this was compared to a fleck mark count carried out on a normal sample of Kenprint paper (sample 2), i.e. paper in which both the emulsion and the supercoat had been hardened with formaldehyde, the paper being processed and glazed similarly. The following results were obtained:

Sample 1--Fleck mark count: less than 25 per square foot. Sample 2-Fleck mark count: more than 500 per square foot.

We claim as our invention:

1.In photographic material suitable for use for the production of glazed prints, which material comprises in the unexposed and unprocessed state a support base having coated on at least one side a gelatino silver halide emulsion layer, the said gelatin having been hardened by the presence of formaldehyde therein, the improvement that there is coated on this layer a gelatin supercoat layer which has been hardened by the presence of mucochloric acid therein, the amount of said acid being from 0.35 to 2% by weight of the gelatin present.

2. Photographic material according to claim 1 wherein the support basey'is a paper base having coated thereon a baryta layer.

3. Photographic material according to claim 1 wherein the amount of mucochloric acid present in the supercoat layer is from 1 to 1.5% by weight of the gelatin present.

4. A process for the production of photographic material suitable for use for the production of glazed prints, which comprises coating on a base support a gelatino silver halide emulsion layer which comprises sufficient formaldehyde to harden the layer, allowing this layer to set and coating on this layer a gelatin supercoat layer which comprises sufficient mucochloric acid to harden the layer and allowing this layer to set and drying the product, the amount of said acid being from 0.35 to 2% by weight of the gelatin present.

5. Glazed photographic prints which have been prepared by exposing, processing and glazing of the photographic material claimed in claim 1.

References Cited UNITED STATES PATENTS 3,295,981 1/1967 Milton 96- 109 3,507,678 4/1970 Shimizu 96-67 3,030,209 4/1962 Henn 96-111 3,128,184 4/1964 Lowe 96-111 FOREIGN PATENTS 663,457 12/1951 Great Britain 96-87 NORMAN G. TORCHIN, Primary Examiner J. R. HIGHTOWER, Assistant Examiner US. Cl. X.R. 96-5O PL, 111 

